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Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2003 December;43(4):459-64

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

Growth trends of dynamic strength in adolescent boys. A 2-year follow-up survey

Kanehisa H. 1, Abe T. 2, Fukunaga T. 3

1 Department of Life Sciences (Sports Sciences), Univesity of Tokyo, Tokyo, Japan 2 Department of Exercise and Sports Science, Tokyo Metropolitan University, Tokyo, Japan 3 Department of Sports Sciences, School of Human Sciences, Waseda University, Tokyo, Japan


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Aim. The ­present ­study ­aims to inves­ti­gate the ­growth ­trends of ­dynamic ­torque ­during ado­les­cence ­through a 2-­year ­follow-up ­survey.
­Methods. Con­cen­tric ­torque ­during ­elbow flex­ions and ­knee exten­sions at 3 con­stant veloc­ities (1.05, 3.14, and 5.24 rad·sec-1) ­were deter­mined ­year-by-­year, i.e., 3 ­times (T1, T2, and T3), ­using an iso­ki­netic dyna­mom­eter in 10 ­boys ­aged 12.7 to 13.5 ­years at the ­start of the ­study. In addi­tion, the ­muscle thick­ness at the ante­rior ­sites of the ­upper arm and ­thigh ­were meas­ured ­using a bright­ness ­mode ultra­sound appa­ratus. For the two ­motions, ­torque ­output at 1.05 rad·sec-1 ­increased sig­nif­i­cantly ­year by ­year, but ­those at 3.14 and 5.24 rad·sec-1 did not ­show sig­nif­i­cant ­changes ­between T2 and T3.
­Results. The ­muscle thick­ness ­showed sig­nif­i­cant dif­fer­ences ­between T1 and T3 for the ante­rior ­upper arm and ­between T3 and ­either T1 or T2 for the ante­rior ­thigh. In ­both ­motions, the ­ratio of ­torque ­output at 1.05 rad·sec-1 to the ­product of ­muscle thick­ness ­squared and ­height was sig­nif­i­cantly ­higher in T2 and T3 ­than in T1. The cor­re­sponding ­ratios in ­elbow flex­ions at 3.14 and 5.24 rad·sec-1 ­were ­also sig­nif­i­cantly ­higher in T2 com­pared to T1, but ­those in the ­knee exten­sions did not ­show sig­nif­i­cant ­effects of age.
Con­clu­sion. ­These ­results indi­cate ­that, for ado­les­cent ­boys, 1) the age-­related ­changes in ­dynamic ­torque at ­high ­velocity con­trac­tions ­differ ­from ­those at ­slow ­velocity con­trac­tions, and 2) the ­growth ­rate of ­dynamic ­torque at ­slow ­velocity con­trac­tions ­exceeds ­that of ­muscle ­size in the ear­lier ­stage of ado­les­cence.

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